This invention relates to measuring devices, and more specifically to a measuring device that is particularly suited for employment for purposes of effecting measurements simultaneously and in situ of the particle size distribution and volumetric density of particles that are present in a fluid substance.
One of the important parameters in many industrial processes is particle size. As such, it has long been known in the prior art to provide devices that are capable of being employed for purposes of effecting measurements of particles. To this end, the prior art is replete with examples of various types of devices that have been used to obtain measurements of particles. In this regard, in many instances discernible differences exist in the technique by which the measurement of the particles is accomplished. The existence of such differences is, in turn, attributable for the most part to the diverse functional requirements that are associated with the specific application in which such devices are designed to be employed. For instance, in the selection of the particular type of device that is to be utilized for a specific application one of the principal factors to which consideration must be given is that of the nature of the substance of which the particle that is to be measured is formed. Another factor to which consideration must be given is that of the nature of the substance in which the particles are present at the time they are being measured. Yet another factor to which consideration must be given is the relative size of the particles that are to be measured.
Some of the techniques that have been utilized heretodate by the prior art for purposes of accomplishing the measurement of particles include acoustical techniques, optical counting techniques, electrical counting techniques, sedimentation techniques, separation techniques and surface measurement techniques. Moreover, the kinds of particles with which such techniques have been sought to be applied for purposes of making measurements of the particles include such particles as blood particles, food particles, chemical particles, mineral particles as well as others. In addition, diverse ones of the techniques to which reference has been had hereinbefore have been sought to be employed for purposes of accomplishing the measurement of particles while the latter are present in a variety of different types of fluid substances such as various types of gases and various types of liquids.
Unfortunately, however, the devices that have been available in the prior art heretofore for purposes of enabling the techniques to be carried out which have been referred to above have been found to be disadvantageously characterized in one or more respects. To this end, where such devices have been sought to be employed in connection with applications involving industrial processes for purposes of generating information relating to particle size that could be utilized to accomplish, as needed, adjustments to the industrial process, it has not been possible through the use of prior art forms of devices to generate the information required in a sufficiently timely fashion and/or with the desired degree of accuracy. Namely, it has proven to take far too long and/or to require far too much effort to generate the desired information pertaining to particle size for this information to be of any significant value insofar as concerns the utilization thereof for purposes of making timely adjustments to the industrial process. In large measure this is based on the fact that with the prior art devices that have heretofore been available for use for purposes of effectuating particle size measurements it has not been possible to make measurements in situ therewith. As a result, in order to make use of the prior art devices that have been available heretofore there has most often existed a need to collect a sample from the medium in which are present the particles that it is desired to measure, a need to transport this sample to the device that is to be used to accomplish the particle size measurements, a need to actually perform the particle size measurements with the device, and then finally based on the results of the particle size measurements effectuate whatever adjustments must be made to the industrial process in order to ensure that the particles do in fact embody the size that they must have if the particular industrial process from which the particles that were measured were taken is to be successfully operated.
By way of exemplification and not limitation, one form of industrial process in which particle size is known to be an important consideration for the successful operation of the process is the combustion of pulverized coal. As regards the combustion of pulverized coal, it has long been known that an essential component of any steam generation system that utilizes pulverized coal as a fuel is the apparatus in which the coal is pulverized in order to render the coal suitable for such usage. One form of apparatus in particular that has frequently been used for purposes of accomplishing the pulverization of coal, although various types of apparatus have been known to have been employed for this purpose, is that which those in the industry commonly refer to as a bowl mill. The bowl mill obtains its name principally from the fact that the pulverization, i.e., grinding, of the coal that takes place therewithin occurs on a grinding surface which in configuration bears a resemblance somewhat to that of a bowl. By way of illustration, reference may be had to U.S. Pat. No. 3,465,971, which issued Sept. 9, 1969 to J. F. Dalenberg et al and which is assigned to the same assignee as the present invention, for a showing of a prior art form of bowl mill. This patent contains a teaching of both the nature of the construction and the mode of operation of a bowl mill that is suitable for use for purposes of effectuating the pulverization of the coal that is used to fuel a coal-fired steam generator.
The efficient combustion of pulverized coal, particularly as it relates to the use of pulverized coal as a fuel in a steam generation system, requires that the coal particle size be held close to a specified particle size distribution. Typically, for a medium reactivity coal this is 70% passing through 200 mesh, and 1% not passing through 50 mesh. Based on an economic evaluation for a typical 500 MW coal-fired steam generator power plant, it has been determined that through an increase in carbon conversion rate which in turn is achievable by maintaining a specified particle size distribution, it is possible to realize significant savings amounting to hundreds of thousands of dollars on an annualized basis in the cost of operating a power plant of the size to which reference has been made hereinbefore. Obviously, however, the savings that will be actually realized insofar as any specific power plant that is fueled with pulverized coal is concerned by virtue of maintaining the coal particle size close to a specified particle size distribution will be dependent on a number of factors including the reaction kinetics of the coal, i.e., how sensitive the combustion efficiency is to particle size for the specific coal being used, and how well and often control is exercised over the bowl mill to maintain the optimum size distribution of the coal particles. In every instance, however, maintaining the size distribution of the coal particles close to the optimum should result in some measure of fuel savings.
Other benefits should also flow from the fact that better control is being exercised over the size distribution of the coal particles. In this regard, reference is had to the fact that there should be reduced slagging in the steam generator due to better control over the size distribution of the coal particles. In addition, it may be possible in some instances to make use of the fact that deviations are occurring in the size distribution of the coal particles from that which should be present as a maintenance and diagnostic aid to detect problems associated with the operation of the bowl mill in which the pulverization of the particles of coal that have been measured was effected. Also, the possibility exists for exercising continuous control over the operation of the bowl mill through the use of the information garnered from having made coal particle size measurements. Yet another possibility is to utilize the information acquired from the performance of coal particle size distribution measurements for purposes of obtaining an indication of the fuel-to-air ratio in the coal feed pipe by means of which, as is well-known to all, the pulverized coal particles are conveyed from the bowl mill to the steam generator wherein the combustion of the pulverized coal particles takes place.
Thus, there has been evidenced in the prior art a need for a new and improved form of particle size measuring device which would embody a mode of operation whereby it would be possible therewith to rapidly obtain an accurate particle size measurement. Namely, a need has been evidenced for a new and improved form of particle size analyzer that would render it possible to provide an on-line measurement of particle size such that the information derived from such measurements is obtained in a timely fashion whereby this information can be utilized for purposes of effectuating control over an industrial process wherein particle size is an important parameter. That is, a new and improved form of particle size analyzer has been sought whereby it would be possible to make measurements therewith in situ of particle size distribution such that adjustments can be had to an industrial process, when such adjustments are deemed to be necessary based on measurements of particle size distribution. In addition, there has been sought such a particle size analyzer which is further characterized in that simultaneous with the making of the particle size distribution measurement, it is also possible therewith to concurrently obtain measurements in situ of volumetric density.
It is, therefore, an object of the present invention to provide a new and improved measuring device that is operative for purposes of obtaining measurements of the size of particles that are present in a fluid substance.
It is another object of the present invention to provide such a new and improved particle size measuring device which renders it possible through the use thereof to rapidly obtain accurate measurements of particle size.
It is still another object of the present invention to provide such a new and improved particle size measuring device through the use of which it is possible to make in situ measurements of the size of particles that are present in a fluid substance.
A further object of the present invention is to provide such a new and improved particle size measuring device that is operative to effect the measurement in situ of the particle size distribution of particles which are present in a fluid substance.
A still further object of the present invention is to provide such a new and improved particle size measuring device that is operative to effect the measurement in situ of the volumetric density of particles that are present in a fluid substance concurrent with the making of measurements in situ of the particle size distribution of the particles which are present in the fluid substance.
Yet another object of the present invention is to provide such a new and improved particle size measuring device which renders it possible through the use thereof to generate information relating to particle size in a sufficiently timely fashion whereby control may be exercised over an industrial process based on the information derived from the particle size measurements.
Yet still another object of the present invention is to provide such a new and improved particle size measuring device which is relatively simple to manufacture and operate, while yet being relatively inexpensive to provide.